---
 Lib/test/test_urlparse.py                                             |   21 ++++++++++
 Lib/urlparse.py                                                       |    9 +++-
 Misc/NEWS.d/next/Library/2022-11-12-15-45-51.gh-issue-99418.FxfAXS.rs |    2 
 3 files changed, 30 insertions(+), 2 deletions(-)

Index: Python-2.7.18/Lib/test/test_urlparse.py
===================================================================
--- Python-2.7.18.orig/Lib/test/test_urlparse.py
+++ Python-2.7.18/Lib/test/test_urlparse.py
@@ -1,4 +1,5 @@
 from test import test_support
+from urlparse import isascii
 import sys
 import unicodedata
 import unittest
@@ -592,6 +593,26 @@ class UrlParseTestCase(unittest.TestCase
         self.assertEqual(p.netloc, "www.example.net:foo")
         self.assertRaises(ValueError, lambda: p.port)
 
+    def do_attributes_bad_scheme(self, bytes, parse, scheme):
+        url = scheme + "://www.example.net"
+        if bytes:
+            if isascii(url):
+                url = url.encode("ascii")
+            else:
+                return
+        p = parse(url)
+        if bytes:
+            self.assertEqual(p.scheme, b"")
+        else:
+            self.assertEqual(p.scheme, "")
+
+    def test_attributes_bad_scheme(self):
+        """Check handling of invalid schemes."""
+        for bytes in (False, True):
+            for parse in (urlparse.urlsplit, urlparse.urlparse):
+                for scheme in (".", "+", "-", "0", "http&"):
+                    self.do_attributes_bad_scheme(bytes, parse, scheme)
+
     def test_attributes_without_netloc(self):
         # This example is straight from RFC 3261.  It looks like it
         # should allow the username, hostname, and port to be filled
Index: Python-2.7.18/Lib/urlparse.py
===================================================================
--- Python-2.7.18.orig/Lib/urlparse.py
+++ Python-2.7.18/Lib/urlparse.py
@@ -31,7 +31,8 @@ test_urlparse.py provides a good indicat
 import re
 
 __all__ = ["urlparse", "urlunparse", "urljoin", "urldefrag",
-           "urlsplit", "urlunsplit", "parse_qs", "parse_qsl"]
+           "urlsplit", "urlunsplit", "parse_qs", "parse_qsl",
+           "isascii"]
 
 # A classification of schemes ('' means apply by default)
 uses_relative = ['ftp', 'http', 'gopher', 'nntp', 'imap',
@@ -68,6 +69,10 @@ _UNSAFE_URL_BYTES_TO_REMOVE = ['\t', '\r
 MAX_CACHE_SIZE = 20
 _parse_cache = {}
 
+# Py3k shim
+def isascii(word):
+    return all([ord(c) < 128 for c in word])
+
 def clear_cache():
     """Clear the parse cache."""
     _parse_cache.clear()
@@ -211,7 +216,7 @@ def urlsplit(url, scheme='', allow_fragm
         clear_cache()
     netloc = query = fragment = ''
     i = url.find(':')
-    if i > 0:
+    if i > 0 and isascii(url[0]) and url[0].isalpha():
         if url[:i] == 'http': # optimize the common case
             scheme = url[:i].lower()
             url = url[i+1:]
Index: Python-2.7.18/Misc/NEWS.d/next/Library/2022-11-12-15-45-51.gh-issue-99418.FxfAXS.rs
===================================================================
--- /dev/null
+++ Python-2.7.18/Misc/NEWS.d/next/Library/2022-11-12-15-45-51.gh-issue-99418.FxfAXS.rs
@@ -0,0 +1,2 @@
+Fix bug in :func:`urllib.parse.urlparse` that causes URL schemes that begin
+with a digit, a plus sign, or a minus sign to be parsed incorrectly.